Search results for "Ketone"

Stereoselektive c-glycosidsynthese durch titan-(iv)-katalysierte addition von silylenolethern an 2-acyloxy-3-keto-glycale

1984

Abstract C-Glycosides are stereoselectively formed by the titan-(IV)-catalysed addition of silyl enolethers 2 to 2,4,6-tri-O-acyl-1-deoxy-D-erythro-hex-1-enopyran-3-uloses 1 followed by elimination of the 4-acyloxy substituent. Cyclohexenyl silylether 2a reacts with 2-acetoxy-3-keto-glycal derivative la forming only one product 3a . Thus, the reaction seems to be diastereospecific with respect to both new chiral centers of the product.

Direct observation and thermal transformations of dications derived from dibenzotropylium ions

1992

Abstract Carboxylic acid 1 and its derivatives 2 , 3 treated with triflic acid below −20°C afford the dications 1H 2+2- 3H 2+2. Cyclodehydration above 20°C (or in the gas-phase, CIMS of 3 ) leads to the diprotonated ketone 4H 2+2.

Solvent quality as reflected in concentration- and temperature-dependent Flory-Huggins interaction parameters

2001

Flory-Huggins interaction parameters (χ) between poly(dimethylsiloxane) (weight-average molecular weight = 152 kg/mol) and various solvents (methyl ethyl ketone, toluene and n-octane) were determined as a function of composition and temperature with vapor-pressure measurements. These data, complemented by independent information for dilute and very concentrated solutions, serve as the basis for a discussion of solvent quality via different theoretical relations. Regardless of polymer concentration, the χ values fall from methyl ethyl ketone via toluene to n-octane, the ketone being the worst solvent and the hydrocarbon being the best solvent. The variation of χ with composition and temperat…

Continuous fractionation and solution properties of PIB. I. Search for the best mixed solvent and first results of the continuous polymer fractionati…

1987

To adopt a recently developed method for large scale fractionation (CPF = continuous polymer fractionation, a special kind of counter current extraction) to polyisobutylene (PIB), a systematic search for the best mixed solvent was performed. For this purpose, the essential parts of the phase diagrams solvent/nonsolvent/PIB were determined for 21 mixed solvents by cloud-point measurements; with eight systems of special interest, the molecular weight distributions of the polymers contained in the coexisting phases were also studied. On the basis of these experiments and of considerations concerning additional criteria for the performance of the continuous counter current extraction, the mixed…

ChemInform Abstract: Enantioselective Addition of Nitromethane to α-Keto Esters Catalyzed by Copper(II)-Iminopyridine Complexes.

2008

The copper complex of a chiral iminopyridine easily prepared from (R)-(−)-fenchone and picolylamine catalyzes the enantioselective Henry (nitroaldol) reaction between nitromethane and α-keto esters. Good yields and modest to good enantioselectivities are obtained for a wide range of α-keto esters, bearing aromatic, alkyl or alkenyl groups attached to the ketone carbonyl group.

1-Cycloundecen-3-in

1988

Es wird ein Syntheseweg fur (E)-1-Cycloundecen-3-in (E-5) beschrieben (Schema 2). Die extrem gespannte Verbindung isomerisiert sich bei Raumtemperatur mit einer Halbwertszeit von 2.2 h (ΔG≠ = 76 kJ/mol). Durch Rotation um die CC-Doppelbindung entsteht dabei (Z)-1-Cycloundecen-3-in (Z-5), das keine geometrische Ringspannung Eg mehr besitzt.

2003

Jerboa (Jaculus orientalis) is a deep hibernating rodent native to subdesert highlands. During hibernation, a high level of ketone bodies i.e. acetoacetate (AcAc) and D-3-hydroxybutyrate (BOH) are produced in liver, which are used in brain as energetic fuel. These compounds are bioconverted by mitochondrial D-3-hydroxybutyrate dehydrogenase (BDH) E.C. 1.1.1.30. Here we report, the function and the expression of BDH in terms of catalytic activities, kinetic parameters, levels of protein and mRNA in both tissues i.e brain and liver, in relation to the hibernating process. We found that: 1/ In euthemic jerboa the specific activity in liver is 2.4- and 6.4- fold higher than in brain, respective…

New dinuclear copper complexes incorporating bis(imidazolyl) based ligands and bidentate–monodentate oxalate bridges. Crystal structure and magnetic …

2016

Abstract This paper reports the synthesis, X-ray crystal structure and magnetic characterization of two novel copper(II) dinuclear compounds including bis(imidazolyl) ligands and oxalate anions, [Cu2(BIM)2(C2O4)2]·4H2O (1) (BIM = bis(2-imidazolyl)methane) and [Cu2(BIK)2(C2O4)2] (2) (BIK = bis(2-imidazolyl)ketone). The oxalate anion acts as bidentate–monodentate in both cases, although it exhibits different coordination bridging modes: whereas in compound 1 a μ1,1,2-oxalato is observed, a μ1,2,3-oxalato is found in compound 2. In both cases, the 3D framework is held together by a combination of H-bonding and aromatic-aromatic interactions provided by the convenient structural features of BIM…

Study of the interaction of [Cu(bipy)]2+ with oxalate and squarate in aqueous solution

1988

A study of the formation of complexes between [Cu(bipy)]2+ and ox2− and sq2− in aqueous solution, (bipy being 2,2′-bipyridine and ox2− and sq2− the dianions of ethanedioic acid and 3,4-dihydroxy-3-cyclobutene-1,2-dione, respectively), has been carried out with the aim of comparing the coordinating properties of these related ligands. The constants of the equilibria (i) and (ii) $$[Cu(bipy)]^{2 + } + ox^{2 - } \rightleftharpoons [Cu(bipy)ox]$$ (i) $$[Cu(bipy)]^{2 + } + sq^{2 - } \rightleftharpoons [Cu(bipy)sq]$$ (ii) have been determined by potentiometry and spectrophotometry at 25.0°C and 0.1 M NaNO3:logβ=5.78(2) and 2.16(2) for the oxalato- and squarato-complex, respectively. Such differen…

A novel photochemical 1,4-acyl migration in enol esters. The photolysis of enol acetates of 3-phenylpropiophenones

1987

Abstract Photolysis of the enol acetates 1a,b gives the 1,4-diketones 4a,b by a mechanism involving a primary homolytic carbonyl—oxygen bond cleavage, followed by 1,2-hydrogen shift and in cage recombination.